METHOD FOR EXTRACTING A YAW BRAKE PISTON
Publication Date: 2013-Jul-10
The IP.com Prior Art Database
The present invention proposes techniques for removing a yaw brake piston from bedplate of a wind turbine. An embodiment of the invention includes creation of threads in the yaw break piston. Another embodiment of the invention also includes creation of threads on inside diameter of the piston. The threads are machined into inside of the piston using a small portable machine. After thread creation in both the embodiments, a device that has mating threads is installed. Once the device is installed, the device is pulled on with great force which liberates yaw piston from the bedplate. Another embodiment of the invention includes milling or machining of a circular groove into inside diameter of the piston. After completion of the groove, a threaded plug is inserted into the piston and a circlip ring is installed into the milled groove. Subsequently, a pulling device is threaded into the plug which reacts against the circlip ring. A great amount of force is exerted onto the piston to free the piston from the bore.
The present invention relates generally to a wind turbine and more particularly to a yaw brake piston assembly in the wind turbine.
A wind turbine bedplate is generally rotatably mounted on a stationary wind turbine tower. The bedplate is connected to a yaw encoder which provides angular position of the bedplate with respect to the stationary tower. A yaw brake assembly keeps the bedplate in its position. The yaw brake assembly generally includes an outer casing mounted within the bed plate of a nacelle, a brake piston movably disposed within the outer casing and a puck or brake pad secured to the bottom of the brake piston. The brake piston is configured to be pushed or pressed against a friction surface of the wind turbine such that the brake pad is maintained in frictional engagement with friction surface as the bedplate and nacelle are rotated about yaw axis.
Usually, the yaw brake piston gets stuck in the bedplate due to tight machining clearances and other external factors, such as, oxidation, gummed-up grease, piston deformation, or mechanical damage. At the bottom of each piston there is a short thread that is utilized to extract the pistons. However, in case significant force is applied to extract the thread, the thread gets easily stripped out.
Several conventional techniques are known in the art that is used for removing yaw brake piston from the bedplate. A conventional technique includes piston cutting using a saw-zaw in order to remove piston from the bedplate. However, the technique is not very safe. Also, the application of such conventional technique damages bore and the bedplate.
Another conventional technique includes utilization of liquid nitrogen. Several attempts are made to shrink yaw piston away from bore. However, handling liquid nitrogen up in wind turbine tower is hazardous. Another conventional technique includes utilization of crow bar. The crow bar is used as leverage under yaw piston. However, crow bar damages yaw bearing and does not extract yaw piston. Yet another conventional technique includes an internal cam locking device. The cam locking devices expand and push aggressively against internal diameter of yaw piston. The cam locking devices are made from soft bronze, thereby, expanding the yaw piston and locking the piston further into bore.
It would be desirable to have a simple and effective technique to extract yaw brake piston from bedplate of a wind turbine.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 depicts yaw brake piston extraction using technique according to an embodiment of the invention.
Figure 2 depicts machining of threads into inside diameter of the piston using small portable machine.
Figure 3 depicts an assembly of threaded rod, pulling table and nut in threaded piston.
Figure 4 depicts yaw brake piston extraction technique according to another embodiment of the invention.
Figure 5 depicts yaw brake piston extraction using technique accord...